History of flood fighting in the Kisosansen River Basin

Takeuchi, Yoichi; Takezawa, Mitsuo; Gotoh, Hiroshi

doi:10.2495/friar080121

Cited by 3 publications

(2 citation statements)

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“…Spur dikes are structures that are built perpendicular or diagonally to the river channel, mainly in the middle and lower reaches of rivers, to prevent riverbank erosion [34]. They were first introduced in Japan by Dutch engineers in the 1800s (Meiji era) and were used for the channelization of large rivers in low-lying areas, like the Kiso River [5,35]. They were later introduced to steep rivers on alluvial fans, like the Kurobe River [36].…”

Section: Spur Dike Applicationsmentioning

confidence: 99%

Spur Dike Applications for the Sustainability of Channels in Incised Steep Bend Streams

Ohtsuki,

Kono,

Arikawa

et al. 2024

Water

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Japan’s rivers are shaped by distinctive topography and abundant rainfall, and they face flooding and sediment supply escalation concerns under climate change. Small- and medium-sized rivers tend to catch unprecedented forces that exceed planned levels, leading to substantial widening and excavation. Thus, there is a demand for a method that is capable of managing significant flood flows over an extended period. The spur dike can maintain channel clearance by promoting erosion as well as providing bank protection. However, the effectiveness of this spur dike function has not been well studied in small- and medium-sized rivers and curved reaches. In this study, we evaluate the function of spur dikes in improving channel sustainability based on examples of small- and medium-sized rivers that have maintained their channel for more than ten years after spur dike installation. First, the applicability of the empirical rule was evaluated by comparing it with actual cases of erosion depths in curved sections in Japan. Next, one-dimensional simulations were performed to evaluate the sustainability of the section over a long period. Finally, a depth-averaged morphodynamic simulation, including the secondary flow effect, was applied to evaluate the location of the flow core and elevation changes due to the spur dike. The results showed that a slight difference in the ratio of river curvature radius to river width (r/B) caused the river channel to be erosive and sedimentary. The reasons for the difference were the cross-sectional expansion caused by the excavation of the bend and the difference in the plane flow regime caused by the shift of the flow core to the inside of the bend. Although it is structurally challenging to reproduce localized scour around a spur dike in a depth-averaged simulation, it is essential for designing to apply the simulation model and combine empirical knowledge.

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Section: Spur Dike Applicationsmentioning

confidence: 99%

Spur Dike Applications for the Sustainability of Channels in Incised Steep Bend Streams

Ohtsuki,

Kono,

Arikawa

et al. 2024

Water

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“…The channel gradient was 0.15% with an average wetted main-channel width of c. 400 m during the base-flow period. The natural functional floodplain of Kiso River has been reduced substantially over the past few hundred years, with constructions of flood dykes that run along both sides of the segment (Takeuchi, Takezawa & Gotoh, 2008). Relatively extensive areas of gravel and sand bars without or with sparse vegetation cover remained within dykes in the 1930s, within which large numbers of floodplain backwaters (i.e.…”

Section: Study Sitementioning

confidence: 99%

Terrestrialization alters organic matter dynamics and habitat quality for freshwater mussels (Unionoida) in floodplain backwaters

et al. 2014

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Summary Anthropogenically induced reduction in flood inundation frequency often leads to terrestrialisation, which accompanies establishment and expansions of tree cover on areas formerly with little or no trees. We tested hypotheses that terrestrialisation degrades habitat for freshwater mussels (Unionoida: Unio douglasiae nipponensis and Lanceolaria grayana) by changing the organic matter (OM) dynamics in floodplain backwaters. Stable isotope composition of seston, periphyton, fine and coarse benthic particulate OM (FBPOM and CBPOM) and mussel tissues was measured to understand OM dynamics and food webs in 14 backwaters in the middle segment of the Kiso River, Japan. Isotope ratios, C : N ratio and chlorophyll a as a proxy of food resource characteristics and the frequency of hypoxia were related to mussel growth rates. δ13C of seston, periphyton and FBPOM was low at sites with lower inundation frequency (a greater degree of terrestrialisation), whereas such a trend was not observed for CBPOM (i.e. riparian leaf litter). Mussels fed exclusively on seston or mixtures of seston and periphyton with their δ13C tracking fluctuations in food resources. Sestonic δ13C differences were attributed to changes in dominant carbon origin from predominantly river‐borne to autochthonous sources, while periphytic δ13C differences were possibly caused by a varying level of dependence on respiratory CO2. FBPOM‐δ13C differences were associated with a greater contribution of CBPOM to the FBPOM pool in infrequently flooded backwaters. Variability in mussel growth was more closely related to hypoxia than food resource characteristics. We inferred that terrestrialisation changes quality of seston and benthic detritus and degrades habitat conditions largely by accumulating riparian leaf litter in the benthic detrital pool and increasing the frequency of hypoxia. The removal of riparian trees may temporarily improve habitat condition in backwaters heavily affected by terrestrialisation. However, ecological integrity in the long run requires the recovery of the process that suppresses terrestrialisation, which includes restoration of incised channels and flood pulses.

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Evolutionary systemic modelling of practices on flood risk

Khatibi

2011

Journal of Hydrology

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History of flood fighting in the Kisosansen River Basin

Cited by 3 publications

References 0 publications

Spur Dike Applications for the Sustainability of Channels in Incised Steep Bend Streams

Spur Dike Applications for the Sustainability of Channels in Incised Steep Bend Streams

Terrestrialization alters organic matter dynamics and habitat quality for freshwater mussels (Unionoida) in floodplain backwaters

Evolutionary systemic modelling of practices on flood risk

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